Patent GB-594893-A (GB)
Title: An improved apparatus for automatic radio-direction-finding, position-finding, and landing of aircraft in weather of restricted or zero visibility
IPC: G01S13/91
Filed: 1945-02-14
Abstract: 594,893. Radio direction-finding and navigation. GRACIAS, H. D. Feb. 14, 1945, No. 3739. [Class 40 (v)] [Also in Groups XX and XXXV] In an automatic radio direction-finder the bearing or elevation is determined through the agency of two electric motors which rotate in opposite directions at speeds proportional to the strength of signals received by separate spaced directional aerials so that resultant rotation of the aerial system occurs until the signals received are of equal strength. A ground station for guiding aircraft to a landing consists essentially of an automatic radio direction- and elevation-finding equipment comprising eight directional aerials 1a-d and 2a-d fixed in pairs at the ends of connecting shafts 8 which are supported by a horizontal bar 3. The whole array is supported by a vertical shaft 6 and may be pointed in any direction by rotation of shaft 6 and bar 3, and the individual aerials are so arranged that their planes of maximum reception are tilted slightly outwards. The array is driven by electric motors in bearing and elevation until approximately maximum reception of the transmission from an aircraft is obtained. Thereafter motor 5 controlled by the signal from aerials 1a, 1b rotates the array about sleeve 4 while motor 7 controlled by the signal from aerials 1c, 1d rotates the sleeve 4 in the opposite direction so that the array assumes a position facing the aircraft with the signal pick-up in both pairs of aerials equal. Motors 9 and 11 similarly driving the shafts 8 and sleeves 10 in opposite direction under the control of the signals from the pairs of aerials 2a, 2b and 2c, 2d, position the array accurately in elevation. The distance of'the aircraft may be observed simultaneously by radiolocation technique using an equipment alternately transmitting and receiving over aerial 15 for short intervals of time under the control of a rotating cam, at a radio frequency differing from that employed for the directional determination. The aircraft carries a responding receiver-transmitter for co-operating with the distance determining equipment. The true bearing of the craft and its reciprocal and also the distance and angle of elevation are continuously indicated on a control panel. The height and ground range obtained from a computer fed with the slant range and elevation are also displayed. The computer also determines, from the aircraft position at different times, the ground speed of the aircraft and enables the speed and course of the craft to be indicated on the control panel. In indicating the height of the aircraft allowance is made for the height of the aerial system which may be increased when working at long ranges. When the aircraft has been directed to the vicinity of the landing ground, which is spaced from the controlling ground station an automatic plotting machine is brought into operation. A transparent sheet 16 has a scale model of the aerodrome and its surroundings shown upon it and a vertical slotted shaft 17 which represents the controlling station is rotated in step with the aerial system and carries two slotted horizontal arms 19, 20 carrying respectively a slotted index 21 and a stylus 22 which are driven by motors to radial positions corresponding to the ground range of the aircraft. The stylus 22 thus indicates the ground position of the aircraft while the height of the index 21 above the sheet 16 is automatically set by a motor to correspond with the height of the aircraft and thus indicate its position in three dimensions. A bearing scale is marked on the sheet 16 and a wire 25 mounted on a spring-loaded reel and attached to the end of the index 21 enables a check to be made upon the elevation and distance data recorded on the control panel. Other indicators enable the height, ground range and magnetic course data to be checked and a speedometer attached to the stylus enables the ground speed also to be checked. If the aircraft which is being directed passes directly over the controlling station contacts are operated by the index when it has closed in between the pillars of the slotted shaft 17 which cause the shaft to be rotated through 180 degrees so that the plotter may continue to record the track. A further aid to the pilot of the aircraft consists in the transmission to the aircraft by television of a picture of the indications on the control panel together with three views of the plotting machine. The television screen in the aircraft is divided into four sections showing : (1) the control panel information, (2) the track and changing position with respect to the controlling station, (3) the angular elevation and height above ground, and (4) an enlarged view of the aerodrome.